"Noel Gallagher told Q magazine October 2008 that this is, "a love song inspired by the meeting of an Angel in Ibiza.""
Bass player Andy Bell told Q magazine that he thinks its about Gallagher's girlfriend and mother of his second child, Sara MacDonald. He added: "Noel can put things in a down-to-earth way that goes right to the core."
Gallagher met MacDonald at a club on Ibiza in 2000.
Ref: https://en.wikipedia.org/wiki/Noel_Gallagher https://www.songfacts.com/facts/oasis/waiting-for-the-rapture